I finally found a specific page reference in the relevant article in Magne Saebø (ed.), Hebrew Bible / Old Testament: The History of Its Interpretation, vol. 2: From the Renaissance to the Enlightenment (Göttingen: Vandenhoeck & Ruprecht, 2008). The article is by Jared Wicks (see here, or here at bottom), "Catholic Old Testament Interpretation in the Reformation and Early Confessional Eras," and there is a brief (2-page) description of Sixtus and his magnum opus. The reference turns out, I think, to be to a reprint edition, from Inter Documentation Co. (Leiden, 1988), which must not have the same page numbers as the 1566-edition available on Google Books. But the reference did give me the general place to look--at the beginning.
In the edition available at Google Books, see pp. 9-10, esp. p. 10a. This section is titled:
On the scriptures and divine authors of the first class [ordo]; section one. Canonical and apocryphal writings, and who their authors are.There are a lot of interesting little details in these pages (not just pp. 9-10, but this entire discussion on the canon), like where Sixtus lists the 24 books of the OT (p. 13), right after he had already listed the same books, but numbering them as 22 (p. 12), with Ruth joined to Judges (and presumably Lamentations joined to Jeremiah, though this is not made explicit: Lamentations is in fact not mentioned at all in the 22-book list). Amazingly, after saying that the 22-book list is "according to the number of the 22 letters (literae) of the Hebrew alphabet," he says about the 24-book list that it is "according to the 24 Hebrew letters [elementa], which result from 21 Jewish characters and from the letter yod, repeated three times because of the reverence for the divine name." He then lists the 24 books with their corresponding Hebrew letter, and the letter yod is listed three times in a row, corresponding to Isaiah, Jeremiah, and Ezekiel. He also notes the similarity to the Greek alphabet (24 letters) and lists the Greek alphabet alongside the Hebrew. Ruth and Lamentations then move locations to take up their position within the five Megilloth (that term is not used) at the very end of the OT.
If you know anything about ancient OT canon lists, you wont be surprised that a listing of 27 books (same books, different enumeration) comes next (p. 14), with the five Hebrew letters with final forms accounting for the increase and allowing Samuel (Regum 1-2), Kings (Regum 3-4), and Chronicles (Paralipomenon 1-2) to count as 2 books a piece. But, now Lamentations (Threnis) is back with Jeremiah, counted as one book, and Nehemiah has been separated from Ezra. Furthermore, Ruth is back in position after Judges, not with the Megilloth, as before (perhaps because the inclusion of Lamentations with Jeremiah already destroyed the Megilloth?), and in general the sequence here is exactly the same as in modern Protestant Bibles.
You will have noticed that none of these lists includes the deuterocanonicals, sort of strange since Sixtus is writing for the purpose of explaining and defending the decisions at Trent, which included these books as fully canonical with all the others. This takes us back to his division of the canonical books into two groups. At the beginning of this whole section, he writes:
The divine or canonical writings (which Greeks call διαθηκό γραφα [? see comment below], that is, Testamentary writings) are those, which according to the tradition of the ancients through the Holy Spirit himself, are believed to be divinely inspired for our learning: whose authority is so great that it would be criminal to doubt their trustworthiness. But the divine and canonical authors are those who, with the Holy Spirit dictating, wrote the canonical writings with so great a firmness of trustworthiness that it would be impious not to believe them most strongly. Concerning their venerable authority, Augustine says these things while writing to Jerome: I have learned to reserve this fear and honor to those authors alone who are called canonical, that I hold most strongly none of them to have erred in writing. But if I ever stumble over anything in them that seems contrary to the truth, I assume nothing other than that the codex is faulty, or the translator did not achieve what was said, or I will not doubt that I have understood poorly. But as for other books I say that however influential in sanctity or doctrine they are, I do not therefore regard them as true because they seem so, but because through the canonical authors themselves, or probable reasons, they do not seem to me to depart from the truth, they can persuade. Thus Augustine. Furthermore the canonical books of the old and new testament are divided into two classes: one is prior and the other is posterior; prior, I say, and posterior not in authority, or certitude, or dignity (for each receives its value and majesty from the same Holy Spirit), but in recognition, or time: by which two things it is the case that one class precedes, the other follows.
The canonical books of the first class, which can be called Protocanonical, are of undoubted trustworthiness; that is, concerning their authority there was no doubt or controversy ever in the catholic Church; but immediately from the beginning of the nascent Church they had been accepted by the common consensus of all orthodox Fathers, and they were adopted for the authoritative confirmation of our faith; of which sort in the old testament are the five books of Moses, and in the new testament the four gospels, but also others similar to these to be named in their own place.
The canonical [books] of the second class (which once were labeled Ecclesiastical, and now are called by us Deuterocanonical) are those concerning which, because not immediately at the very times of the Apostles but long afterwards they came to the notice of the entire Church, there was at times among Catholics an undecided opinion [sententia anceps]; for example, in the old testament they are the books of Esther, Tobit, Judith, and Baruch, the epistle of Jeremiah, wisdom of Solomon, Ecclesiasticus, the prayer of Azariah, the Hymn of the three boys, the story of Susanna, the story of Bel, the first book of Maccabees, and the second. Likewise also in the new Testament, the last chapter of Mark, the story of Luke concerning the blood-like sweat of Christ and the appearance of the angel, the story of John concerning the adulterous woman, the epistle to the Hebrews, the epistle of James, the second epistle of Peter, the second epistle of John and the third, the epistle of Jude, the Apocalypse of John, and other books of the same sort, which once the former fathers of the Church had as apocryphal and not canonical; and those they permitted to be read first among catechumens alone, being not yet competent of the canonical lection, as Athanasius testifies in the Synopsis. Then, after some time, as Rufinus writes in the Symbolum, among all the faithful they concede [them] to be read, not for the confirmation of doctrines, but merely for the instruction of the people; and because they are read publicly in the church, they call them Ecclesiastical. But finally they wished [them] to be taken up into the writings of irrefutable authority.
But the apocrypha, that is hidden, secret, or dubious writings, are mentioned in two ways: On the one hand, because their author is uncertain, in which way, of course, it can happen also that some of the canonical books are apocryphal, because it is not at all certain to the church or ascertained who of people was their author, though she believes most confidently that the holy spirit was their author. On the other hand, for a second reason they are called apocrypha, that is of hidden, unknown, uncertain, obscure authority, because the ecclesiastical fathers did not certainly know nor attempt to determine whether they were written by the very authors through the inspiration of the holy spirit; and therefore they did not wish them to be brought forward either for the confirmation of the doctrines of the christian faith or to be read for the edification of the common people, and to be proclaimed in temples, but privately, and they permitted [them] to be read only at home. Such are the third and fourth books of Ezra, the third and fourth book of Maccabees, also the Appendix of the book of Esther, the Appendix of the book of Job, the Appendix of the Psalter, the Appendix of Chronicles, and writings like these, which we have thrown into the third Section. It is also customary in decretals of Pontiffs for the name of an apocryphon occasionally to be placed among the forbidden and completely condemned writings of heretics. This signification we do not use in the present case, because in the common Bibles of catholics we believe no part to be what the apostolic Church pronounced heretical or forbade for christians. Since therefore the entire corpus of the Bible which exists now among catholics is distinguished by a threefold division of books, that is canonical of the first class, canonical of the second class, and apocryphal: we will begin from the enumeration and multiple partition of the canonical volumes of the first class, which are contained in the old testament among us and among the hebrews, then we will treat the books of the first call which the scripture of the new testament embraces.Wow. All of that is just absolutely fascinating. I'm especially surprised, nay, shocked, to see Sixtus talk about the deuterocanonical portions of the NT. I don't think I had ever heard of this. And even things like Mark 16:9-20 and John 7:53-8:11 and Luke 22:43-44 count as deuterocanonical! Wow, fascinating. In the following pages (pp. 11-68) Sixtus goes on to give descriptions of each book, and when he gets to the NT, he lists and discusses first the protocanonical portions and books, numbering 20 (pp. 36-41), and then, after discussing the deuterocanonical OT (pp. 42-48), he lists and discusses the deuterocanonical NT (pp. 48-53), numbering 10: the seven disputed books and the three passages from Mark, Luke, and John.
Out of all the things I'd like to discuss further, let me just mention one minor point. Sixtus says that the Greeks call the canonical books διαθηκό γραφα, or at least that's the way the old and slightly smudged lettering looks to me. This is close to the way Origen a couple times refers to books of scripture as ἐνδιάθηκοι γράφαι (On Prayer 14.4; and in Eusebius, Eccl. Hist. 6.25.1). The term is actually not very common among the Greeks, though Eusebius himself does use it a few times in his Ecclesiastical History (3.3.1, 3; etc.). Sixtus cites a garbled form of the term, making it probable that he has simply heard about this, maybe not even seen it in writing, and it may be doubted whether Sixtus knew much Greek at all. If he knew very little he would not be unique among European biblical scholars in the sixteenth century.